Thermoplastic elastomer composition

ABSTRACT

The present invention provides a thermoplastic elastomer composition having high thermal resistance. It comprises a thermoplastic graft copolymer of which main chain is constituted by a polymer having a glass transition temperature of 10° C. or blow and side chain is constituted by an aromatic oligomer having a flow temperature of 100° C. or above, and an olefinic polymer.

FIELD OF ART

This invention relates to a thermoplastic elastomer composition havinghigh thermal resistance.

BACKGROUND ART

The thermoplastic elastomers (hereinafter abbreviated as TPE) which areindustrially used at present can be roughly divided into two types: TPEcomprising a block copolymer composed of soft segments and hard segmentsand TPE, called elastomer alloy, comprising a partially crosslinkedrubber and a plastic phase-separated therefrom. As the former type,there are known, for instance, the block copolymers called polyesterelastomers consisting of an aliphatic polyether portion such aspolytetramethylene glycol and a polyester portion such as polyethyleneterephthalate and polybutylene terephthalate, and the block copolymerscalled polyamide elastomers consisting of an aliphatic polyether portionand a polyamide portion such as polydodecanolactum. As the latter type,there are known, for example, the elastomer alloys comprising adynamically vulcanized alloy of polypropylene and anethylenepropylene-diene terpolymer.

Also, European Patent Laid-Open No. 0287233 discloses a polymer solutionfor coating using a copolymer having an aromatic polyester as branchpolymer, namely a copolymer having an aromatic polymer covalently bondedto an acrylic resin or polyester resin, said polymer solution beingcharacterized by being capable of forming a coat with high hardness.However, this European patent is silent on thermoplastic resins and TPE.

It is to be noted that with TPE's comprising a block copolymer composedof soft and hard segments, it is merely possible to obtain relativelyhard elastomer having a Shore hardness (D scale) of about 40 or greater.Also, these TPE's take a large compression set and are not so high inthermal resistance.

On the other hand, the elastomer alloys, although capable of forming thesoft elastomers having a Shore Scale A hardness of about 30, are ratherpoor in thermal resistance.

The object of the present invention is to provide a resin compositionuseful as a thermoplastic elastomer with excellent thermal resistance.

DISCLOSURE OF THE INVENTION

In view of these circumstances, the present inventors have pursuedfurther studies on the subject matter and, as a result, found out acomposition containing a thermoplastic graft copolymer comprising apolymer having a glass transition temperature of 10° C. or below as mainchain and a specific aromatic oligomer as side chain, and an olefinicpolymer. It was further found that said composition had the excellentproperties as a thermoplastic elastomer. These findings have led to theattainment of the present invention.

Thus, the present invention pertains to a thermoplastic elastomercomposition containing a thermoplastic graft copolymer comprising apolymer having a glass transition temperature of 10° C. or below as mainchain and an aromatic oligomer having a flow temperature defined belowof 100° C. or above as side chain, and an olefinic polymer.

Flow temperature: the temperature at which the oligomer shows a meltviscosity of 48,000 poises when the oligomer is melted by heating at arate of 4° C./min and extruded from a nozzle of 1 mm in inner diameterand 10 mm in length under a load of 100 kg/cm².

The main chain (backbone polymer) constituting the graft copolymer ofthis invention is the one having a glass transition temperature of 10°C. or below, preferably 0° C. or below, more preferably -10° C. orbelow. The "glass transition temperature" referred to herein means thesecondary transition point at which absorption of heat is observed atthe heating rate of 10° C./min in a differential scanning calorimeter(DSC). If the glass transition temperature (which may hereinafter beabbreviated at Tg) of said main chain (backbone polymer) exceeds 10° C.,the produced thermoplastic elastomer composition of this invention mayfail to show rubber elasticity in the working temperature range abovenormal temperature.

As preferred examples of the main chain (backbone polymer) having Tg of10° C. or below constituting the graft copolymer of this invention,there can be mentioned olefin polymers, conjugated diene polymers andvinyl polymer, namely, homopolymer and random copolymers such as acrylicester polymers, styrene-butadiene copolymer and the hydrogenated productthereof, styrene-isoprene copolymer and the hydrogenated productthereof, polybutadiene, polyisoprene, ethylene-propylene copolymer,ethylene-propylene-diene terpolymer, acrylonitrile-butadiene copolymerand the hydrogenate product thereof, polychloroprene, ethylene-acrylicester copolymer, homopolymers such as chlorosulfonated polyethylenes;organopolysiloxanes, polyphosphazene and the like. It is also possibleto use the copolymers of the monomers constituting said homopolymers orrandom copolymers and the copolymerizable monomers having unsaturateddouble bonds. In any of these copolymers, however, the copolymercomposition must be controlled so that Tg thereof will become 10° C. orbelow.

The side chain aromatic oligomer constituting the graft copolymer ofthis invention is an aromatic oligomer having a flow temperature of 100°C. or above, preferably 150° C. or above. An aromatic oligomer having aflow temperature of 170° C. or above is more preferred. Also, the flowtemperature of said aromatic oligomer should not be higher than 400° C.,preferably not higher than 350° C., more preferably not higher than 300°C.

When the flow temperature of said aromatic oligomer is lower than 100°C., the temperature range in which the obtained thermoplastic elastomercomposition shows rubber elasticity is narrowed, that is, saidthermoplastic elastomer composition becomes unsatisfactory in thermalresistance.

The aromatic oligomer having a flow temperature of 100° C. or above,which constitutes the graft copolymer of this invention, is an oligomerhaving a benzene ring in the main sequence, preferably an oligomercontaining 50% by weight or more, preferably 60% by weight or more ofthe structural units represented by the following formula (1): ##STR1##wherein X is selected from O and S, and the structural unit containing Oand the structural unit containing S may both be contained in oneoligomer; and Ar is selected from the following formulae (2), (3) and(4): ##STR2## wherein R¹ and R² are each selected from an alkyl grouphaving 1 to 3 carbon atoms or a phenyl group; R¹ and R² may be a same ordifferent groups, and the different groups may be attached to onebenzene ring; and p and q are each an integer of 0 to 2.

The number-average degree of polymerization of said oligomer is 2 to 10,preferably 3 to 8, more preferably 4 to 7.

The number-average molecular weight of said oligomer is preferably inthe range of 300 to 1,500, more preferably 400 to 1,000. When thenumber-average molecular weight of said oligomer is less than 300, thepolycondensate becomes prone to be thermally decomposed and its flowtemperature also lowers excessively, resulting in poor thermalresistance of the obtained graft copolymer. When said number-averagemolecular weight exceeds 1,500, the flow temperature approaches thethermal decomposition temperature of said oligomer, which deterioratesmoldability of the obtained thermoplastic elastomer composition.

Said oligomer mainly composed of a hydroxyarylcarboxylic acid polymermay contain a structure in which a monomer such ashydroxyalkylcarboxylic acid, aminoalkylcarboxylic acid,aminoarylcarboxylic acid or the like has been polycondensed or astructure in which a monofunctional carboxylic acid compound, a phenolcompound or an amino compound has been condensed, for controlling theproperties such as melting point of the oligomer.

The reason why the thermoplastic elastomer composition of this inventionshows rubber elasticity is assumed to be that the side chain aromaticoligomer of the graft copolymer constituting said composition functionsas hard segment in the graft copolymer to form a microdomain structureand serve as physical cross-linking points. This supposition, however,is in no way restrictive to the present invention.

The ratio of the polymer having Tg of 10° C. or below to the aromaticoligomer having a flow temperature of 100° C. or above in the graftcopolymer constituting the thermoplastic elastomer of this invention is99:1 to 50:50 (by weight), preferably 97:3 to 65:35 (by weight).

When the ratio of the polymer having Tg of 10° C. or below exceeds 99%by weight, the obtained thermoplastic elastomer composition is subjectto excessive plastic deformation in the temperature range above roomtemperature, and when said ratio is less than 50% by weight, saidcomposition may fail to show desired rubber elasticity.

Said graft copolymer may be used singly as a thermoplastic elastomer,but by blending a polymer containing an olefinic polymer with said graftcopolymer, it becomes possible to improve melt fluidity and thus improvemoldability, without impairing the properties as a thermoplasticelastomer.

The olefinic polymers usable in this invention include homopolymers suchas polyethylene and polypropylene, copolymers such as ethylene-propylenecopolymer, ethylene-butene copolymer and ethylene-propylene-dieneterpolymer, and copolymers of the olefin monomers composing saidhomopolymers or copolymers and copolymerizable monomers havingunsaturated double bonds, such as ethylene-methyl acrylate copolymer,ethylene-ethyl acrylate copolymer, etc. These olefinic polymers may beeither amorphous or crystalline.

Among them, polyethylene, polypropylene, ethylene-propylene copolymerand ethylene-methyl acrylate copolymer are preferred.

Also, the olefinic polymer used in this invention is preferably apolymer containing 30% by weight or more of ethylene and/or propylene.Said olefinic polymer preferably has a glass transition temperature of10° C. or below.

The ratio of the graft copolymer to the olefinic polymer in thethermoplastic elastomer composition of this invention is 99:1 to 50:50(by weight), preferably 95:5 to 70:30 (by weight). When the ratio of thegraft copolymer exceeds 99% by weight, melt fluidity of the compositionbecomes unsatisfactory, and when said ratio is less than 50% by weight,the physical crosslinking points of the side chain (aromatic oligomer)are lessened in number and the obtained thermoplastic elastomercomposition does not show rubber elasticity.

Further, the thermoplastic elastomer of this invention may be properlyblended with a filler such as carbon black, silica, calcium carbonate,mica, diatom earth, zinc white, basic magnesium carbonate, aluminumsilicate, titanium dioxide, talc, glass fiber, silica-alumina fiber,etc., a plasticizer, an antiaging agent, a colorant, an ultravioletabsorber, a flame retardant, an oil resistance improver, a scorchretarder, a tackifier, etc.

As for the way for producing the graft copolymer constituting thethermoplastic elastomer of this invention, there can be mentioned amethod in which a polymer having a glass transition temperature of 10°C. or below and possessing a functional group reactable with carboxylgroup is reacted with an aromatic oligomer having a flow temperature of100° C. or above and possessing a carboxyl group at one terminal of themolecule. As examples of the functional groups reactable with carboxylgroup, there can be cited epoxy group, isocyanate group and acetoxylgroup. Epoxy group is especially preferred.

As the polymer containing epoxy group, there can be mentioned methylacrylate-glycidyl methacrylate copolymer, ethyl acrylate-glycidylmethacrylate copolymer, propyl acrylate-glycidyl methacrylate copolymer,butyl acrylate-glycidyl methacrylate copolymer, hexyl acrylate-glycidylmethacrylate copolymer, dodecyl acrylate-glycidyl methacrylatecopolymer, and the like.

There can also be mentioned methyl acrylate-glycidylstyrene copolymer,ethyl acrylate-glycidylstyrene copolymer, propylacrylate-glycidylstyrene copolymer, butyl acrylate-glycidylstyrenecopolymer, hexyl acrylate-glycidylstyrene copolymer, dodecylacrylate-glycidylstyrene copolymer, and the like.

There can further be mentioned methylacrylate-N-[4-(2,3-epoxypropoxy)-3,5-dimethylbenzyl]acrylamidecopolymer, ethylacrylate-N-[4-(2,3-epoxypropoxy)-3,5-dimethylbenzyl]acrylamidecopolymer, propylacrylate-N-[4-(2,3-epoxypropoxy)-3,5-dimethylbenzyl]acrylamidecopolymer, butylacrylate-N-4-(2,3-epoxypropoxy)-3,5-dimethylbenzyl]acrylamide copolymer,hexyl acrylate-N-[4-(2,3-epoxypropoxy)-3,5-dimethylbenzyl]acrylamidecopolymer, dodecylacrylate-N-[4-(2,3-epoxypropoxy)-3,5-dimethylbenzyl]acrylamidecopolymer, and the like.

There can additionally be mentioned acrylonitrile-butadiene-glycidylmethacrylate terpolymer, acrylonitrile-butadiene-glycidylstyreneterpolymer,acrylonitrile-butadiene-N-[4-(2,3-epoxypropoxy)-3,5-dimethylbenzyl]acrylamideterpolymer, and the like.

There can also be mentioned ethylene-vinyl acetate-glycidyl methacrylateterpolymer, ethylene-vinyl acetate-glycidylstyrene terpolymer,ethylene-vinylacetate-N-[4-(2,3-epoxypropoxy)-3,5-dimethylbenzyl]-acrylamideterpolymer, and the like.

There can further be mentioned ethylene-methyl acrylate-glycidylmethacrylate terpolymer, ethylene-ethyl acrylate-glycidyl methacrylateterpolymer, ethylene-propyl acrylate-glycidyl methacrylate terpolymer,ethylene-butyl acrylate-glycidyl methacrylate terpolymer, ethylene-hexylacrylate-glycidyl methacrylate terpolymer and ethylene-dodecylacrylate-glycidyl methacrylate terpolymer, and the like.

There can further be mentioned ethylene-methyl acrylate-glycidylstyreneterpolymer, ethylene-ethyl acrylate-glycidylstyrene terpolymer,ethylene-propyl acrylate-glycidylstyrene terpolymer, ethylene-butylacrylate-glycidylstyrene terpolymer, ethylene-hexylacrylate-glycidylstyrene terpolymer, ethylene-dodecylacrylate-glycidylstyrene terpolymer, and the like.

There can also be mentioned ethylene-methylacrylate-N-[4-(2,3-epoxypropoxy)-3,5-dimethylbenzyl]-acrylamideterpolymer, ethylene-ethylacrylate-N-[4-(2,3-epoxypropoxy)-3,5-dimethylbenzyl]acrylamideterpolymer, ethylene-propylacrylate-N-[4-(2,3-epoxypropoxy)-3,5-dimethylbenzyl]acrylamideterpolymer, ethylene-butylacrylate-N-[4-(2,3-epoxypropoxy)-3,5-dimethylbenzyl]-acrylamideterpolymer, ethylene-hexylacrylate-N-[4-(2,3-epoxypropoxy)-3,5-dimethylbenzyl]acrylamideterpolymer, ethylene-dodecylacrylate-N-[4-(2,3-epoxypropoxy)-3,5-dimethylbenzyl]acrylamideterpolymer, and the like.

There can also be mentioned styrene-butadiene-glycidyl methacrylateterpolymer, styrene-butadiene-glycidylstyrene terpolymer,styrene-butadiene-N-[4-(2,3-epoxypropoxy)-3,5-dimethylbenzyl]acrylamideterpolymer and the like.

These copolymers can be usually obtained by well-known radicalpolymerization.

The aromatic oligomers having a flow temperature of 100° C. or above,preferably 150° C. or above, and possessing a carboxyl group at oneterminal of the molecule, which are used in the present invention, arepreferably those represented by the following formula (5): ##STR3##wherein X is selected from O and S, and the structural unit containing Oand the structural unit containing S may be both contained in oneoligomer at the same time; n is a number average, which is 2 to 10; R¹⁰is an alkyl group having 5 or more carbon atoms or an aryl or aralkylgroup having 6 or more carbon atoms; and Ar is selected from the generalformulae (6), (7) and (8): ##STR4## wherein R¹ and R² are each selectedfrom an alkyl group having 1 to 3 carbon atoms and a phenyl group, butR¹ and R² may be a same or different groups, and the differentsubstituents may be attached to the same benzene ring; p and q are eachan integer of 0 to 2.

Said oligomers may be copolymerized with a hydroxycarboxylic acid having2 to 6 carbon atoms. The number-average molecular weight of saidaromatic oligomers having a carboxyl group at one terminal of themolecule is preferably in the range of 300 to 1,500, and theirnumber-average degree of polymerization, which depends on what areselected for R¹⁰, R¹, R² and Ar, is 2 to 10, preferably 3 to 8, morepreferably 4 to 7.

The hydroxyarylcarboxylic acid polymer can be produced by any availablemethod as far as it is capable of forming a polycondensate by using asstarting material a hydroxyarylcarboxylic acid and, if necessary, asmall quantity of a copolymerizable monomer such as ahydroxyalkylcarboxylic acid, an aminoalkylcarboxylic acid, anaminoarylcarboxylic acid, which have 2 to 6 carbon atoms, amonofunctional phenol compound, a carboxylic acid compound, an aminocompound or the like. It is, however, recommended to use the followingmethod.

An acetylating agent such as acetic anhydride or acetyl chloride isadded to a hydroxyarylcarboxylic acid, and the mixture is heated andstirred to obtain an acetoxyarylcarboxylic acid. In the above reaction,in case of acetylating the hydroxyarylcarboxylic acid, etc., with aceticanhydride, acetylation can be accomplished by carrying out the reactionat 100° C. or above for 15 minutes or more, and in case of using acetylchloride, acetylation can be attained by conducting the reaction at roomtemperature or above for 30 minutes or more. In either reaction, it isdesirable that acetic anhydride or acetyl chloride be added in an excessamount, preferably about 1.1 mole to one mole of the hydroxyl group tobe reacted. After acetylation has been completed, the reaction system isheated and acetic acid is distilled away with stirring to let thepolycondensation reaction proceed on. The temperature of the reactionsystem needs to be raised to preferably 200° C. or above. Thenumber-average molecular weight can be controlled by adjusting theamount of acetic acid distilled away. For controlling the polymerizationdegree to the desired level, it is necessary to calculate the amount ofthe monomer such as hydroxyarylcarboxylic acid supplied and the amountof acetic acid to be distilled away.

The aromatic oligomers containing a mercaptoarylcarboxylic acid can beproduced in the same way as described above.

The obtained aromatic oligomer is preferably washed with a solvent suchas methanol, ethanol, acetone, tetrahydrofuran, N-methylpyrrolidone,chloroform, pyridine or the like to remove the monomer and dimer forimproving heat stability of the oligomer.

As for the aromatic oligomers having a carboxyl group at one terminal ofthe molecule, a mixture of a monocarboxylic acid having an alkyl groupof 5 or more, preferably 5 to 20 carbon atoms, or an aryl group of 6 ormore, preferably 6 to 15 carbon atoms, a hydroxyarylcarboxylic acid and,if necessary, a hydroxycarboxylic acid of 2 to 6 carbon atoms isacetylated with acetic anhydride or acetyl chloride in the same way asthe above-described preparation of a hydroxyarylcarboxylic acid polymerand then acetic acid is distilled away to obtain a polycondensate. Inthis reaction, the number-average molecular weight is decided by themolar ratio of the monocarboxylic acid to the hydroxycarboxylic acid.

The obtained oligomer having a carboxyl group at one terminal of themolecule is preferably washed with a solvent such as methanol, ethanol,acetone, tetrahydrofuran, N-methylpyrrolidone, chloroform, pyridine orthe like for the same reason as stated above.

The thermoplastic elastomer of this invention can be obtained byreacting a polymer having Tg of 10° C. or below and possessing afunctional group reactable with carboxyl group and an aromatic oligomerhaving a flow temperature of 100° C. or above and possessing a carboxylgroup at one terminal of the molecule to obtain a graft copolymer, andmixing this graft copolymer with an olefinic polymer, or by mixing apolymer having Tg of 10° C. or below having a functional group reactablewith carboxyl group with an olefinic polymer, and reacting this mixturewith an aromatic oligomer having a flow temperature of 100° C. or aboveand possessing a carboxyl group at one terminal of the molecule, or bymixing and reacting all at once a polymer having Tg of 10° C. or belowand possessing a functional group reactable with carboxyl group, anaromatic oligomer having a flow temperature of 100° C. or above andpossessing a carboxyl group at one terminal of the molecule and anolefinic polymer. The way of reaction and/or mixing is not specificallydefined, but a method is recommended in which reaction and/or mixing iseffected by melt kneading.

This melt kneading can be accomplished by using an ordinary kneader ator above the higher one of the melting temperatures (flow temperature inthe case of an aromatic oligomer and melting point in case the olefinicpolymer is a crystalline polymer) of the polymers existing in the systemat the time of kneading. As the kneader, there can be used any type ofkneading means as far as it is capable of exerting high shearing forceat high temperatures, such as Banbury mixer, single-screw extruder,twin-screw extruder, roll mill, kneader, etc.

The reaction or mixing temperature is preferably above the meltingtemperature of the polymer showing the highest melting temperature amongthe polymers existing in the system at the time of kneading and belowthe thermal decomposition temperature of the polymer showing the lowestthermal decomposition temperature among the polymers existing in thesystem. If the reaction and/or mixing temperature is below the meltingtemperature of the polymer showing the highest melting temperature amongthe polymers existing in the system at the time of kneading, there maynot take place the reaction between the carboxyl group of the aromaticoligomer and the polymer having Tg of 10° C. or below, or the olefinicpolymer may not be mixed well. Also, if the reaction and/or mixingtemperature is above the thermal decomposition temperature of thepolymer showing the lowest thermal decomposition temperature among thepolymers existing in the system at the time of kneading, decompositionof said polymer will progress considerably during kneading to exertadverse effects.

For reacting a polymer having Tg of 10° C. or below and possessing afunctional group reactable with carboxyl group and an aromatic oligomerhaving a flow temperature of 100° C. or above and possessing a carboxylgroup at one terminal of the molecule, that is, for promoting grafting,it is desirable to use the highest possible temperature within theabove-defined range. Also, the longer the reaction time and the greaterthe shearing force, the more effective for said purpose.

For further promoting grafting, it is recommended to use a phosphinetype catalyst such as triphenylphosphine, triparatolylphosphine,trimetatolylphosphine, triorthotolylphosphine,tri-2,6-dimethoxyphenylphosphine, etc., or an amine type catalyst suchas 2-phenylimidazole, 2-undecylimidazole,2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-S triazine,1,8-diazabicyclo(5,4,0)undecene-7, etc.

The thermoplastic elastomer composition of this invention can beimproved in melt fluidity without impairing rubber elasticity. Also, itshows the behavior as an excellent rubber elastomer at high temperaturesand is also excellent in thermal resistance and very useful.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is described in further detail below withreference to the examples thereof. The present invention, however, is inno way limited by these examples.

The conditions used for determination of various properties are asdescribed below.

TENSILE TEST

Measurement was made according to ASTM D-638 by using a tensile testerTensilon EM-500 mfd. by Toyo Baldwin Co., Ltd.

COMPRESSION SET TEST

Compression set was measured according to JIS K-6301 by using aconstant-strain compression tester mfd. by Toyo Seiki Seisaku-sho, Ltd.

SHORE HARDNESS

It was measured according to ASTM D-2240 by using a Shore hardnesstester mfd. by Toyo Seiki Seisaku-sho, Ltd. Sample thickness was 4.2 mm.Measurement was made at intervals of 15 seconds.

FLOW TEMPERATURE

By using a Koka-type flow tester CFT-500 mfd. by Shimadzu Corp., thetest oligomer was melted by heating at a rate of 4° C./min and extrudedfrom a nozzle of 1 mm in inner diameter and 10 mm in length under a loadof 100 kg/cm², and the temperature at which the molten oligomer showed amelt viscosity of 48,000 poise was expressed as flow temperature.

MELT INDEX (which may hereinafter be abbreviated as MI)

Measurement was made by a melt indexer mfd. by Toyo Seiki seisaku-sho,Ltd.

Examples 1-3 and Comparative Example 1

An ethylene-methyl acrylate-glycidyl methacrylate terpolymer(ethylene/methyl acrylate/glycidyl methacrylate=35/63/2 (ratio byweight); MI at 190° C. under a load of 2.16 kg=8.7 g/10 min) wasobtained according to the method described in Japanese PatentApplication Kokai No. 61-127709, Example 5.

The glass transition temperature of this polymer was measured by astand-alone differential scanning calorimeter DSC-50 mfd. by ShimadzuCorp., in a nitrogen atmosphere at a heating rate of 10° C./min. Theheat absorption starting temperature was determined by the tangentialmethod from the obtained chart in the usual way, and the determinedtemperature was expressed as glass transition temperature. The thusdetermined glass transition temperature (of the polymer) was -33.7° C.Also, the weight loss on heating of this polymer was measured by astand-alone thermogravimetric analyzer TGA-50 mfd. by Shimadzu Corp., ina nitrogen atmosphere at a heating rate of 10° C./min. It was found fromthe above measurement that this polymer was thermally stable to atemperature close to 350° C.

Then an aromatic oligomer having a carboxyl group at one terminal of themolecule was synthesized in the following way. 0.4 mol (48.8 g) ofbenzoic acid, 0.8 mol (110.4 g) of parahydroxybenzoic acid and 0.88 mol(90 g) of acetic anhydride was supplied into a 500 ml separable flaskequipped with an anchor-shaped agitator, a three-way stop cock and aDimroth condenser. A Teflon sheet cut to a proper size was used aspacking between the upper and lower portions of the flask. Theanchor-shaped agitator was operated at 120 r.p.m. and nitrogen wasintroduced into the reaction system through the three-way stop cock toplace the system under a nitrogen atmosphere while cooling water waspassed into the Dimroth condenser. In this state, the separable flaskwas placed in an oil bath and the oil bath was heated to 160° C. Withthe oil bath kept at 160° C., an acetylation reaction was carried outfor 2 hours under refluxing of acetic anhydride. Upon completion of theacetylation reaction, the Dimroth condenser was quickly replaced with aLiebig condenser and the oil bath was heated to 260° C. The timerequired for raising the temperature from 160° C. to 260° C. was about40 minutes. Thereafter, the oil bath temperature was kept at 260° C. andacetic acid and acetic anhydride released away from the system wererecovered by the Liebig condenser. Recovery of acetic acid, etc., wasstarted after replacement of the Dimroth condenser with a Liebigcondenser, and polycondensation was ended at the point when 104 g ofacetic acid, etc., was recovered in about one hour.

After completion of polycondensation, the oligomer was taken out andpulverized by a pulverizer. There was obtained 130 g of powder. Thispowder was washed with 10 times as much amount (1,300 g) of methanol asfollows to remove the low-molecular weight matter soluble in methanol.130 g of said powder and 1,300 g of methanol were fed into a 2-litreseparable flask, and after setting an anchor-shaped agitator and aDimroth condenser to the flask, this separable flask was placed in anoil bath of 80° C. so that methanol could reflux in the system, andwashing was conducted for one hour under reflux of methanol. Upon theend of washing, the product was filtered and the oligomer was recovered.Further, the recovered oligomer was dried by a vacuum dryer at 80° C.for 10 hours to obtain an aromatic oligomer having a carboxyl groupalone at one terminal of the molecule. There was obtained 85.8 g ofoligomer in a yield of 66%.

The flow temperature of this purified oligomer was measured, finding itwas 182° C. Then weight loss on heating of this purified oligomer wasmeasured by the above-mentioned apparatus TGA-50 in a nitrogenatmosphere at a heating rate of 10° C./min. It was consequently foundthat this purified oligomer was stable to a temperature close to 300° C.

Next, the result of determination of the molecular weight distributionof this purified oligomer is shown below.

In order to closely determine the number-average molecular weight ofsaid aromatic oligomer, its number-average molecular weight was decidedby the chemical decomposition method described below. The "chemicaldecomposition method" referred to herein is a method in which esterlinkage of said aromatic oligomer is chemically severed and decomposedinto monomer units in N-methyl-pyrrolidone (solvent) by usingn-butylamine as decomposing agent, then the decomposed components areidentified and quantified by liquid chromatography and thenumber-average degree of polymerization is determined from the number ofthe terminal groups.

More specifically, 50 mg of said oligomer was supplied into an egg planttype flask containing 40 ml of N-methylpyrrolidone and 10 ml ofn-butylamine, and after connecting a condenser to the flask,decomposition was carried out in an oil bath of 80° C. under stirring bya magnetic stirrer for 12 hours, and thereby said oligomer wasdecomposed into N-n-butylbenzamide, N-n-butyl-p-hydroxybenzamide andp-hydroxybenzoic acid, and after evaporating away excess n-butylamine,the residue was filtered by a membrane filter with a pore side of 0.45microns to prepare a test sample.

Measurement was made by using a high-performance liquid chromatographicsystem mfd. by Tosoh Co., Ltd. (pump: TOSOH CCPM; pump controller: TOSOHPX-8010 (used at measuring wavelength of 254 nm); recorder:CHROMATO-RECORDER 12 mfd. by System Instruments Co., Ltd.; column: TOSOHTSK-Gel ODS-120T), and each component was eluted and quantifiedaccording to the water-methanol gradient elution method.

The water used as solvent was a 1,000:5 (by volume) mixture of ionexchange water and acetic acid, and the methanol used in the aboveelusion was a 1,000:5 (by volume) mixture of methanol of electronicindustrial grade produced by Sumitomo Chemical Industries Co., Ltd. andacetic acid. As for the gradient conditions, measurement was made at anaqueous concentration of 75 vol % for 0 minute, 60 vol % for 30 minutes,0 vol % for 50 minutes and 75 vol % for 60 minutes (concentration wasvaried rectilinearly in each case).

Quantification of the respective components contained in said sample,conducted under the above-said conditions, gave the result ofparahydroxybenzoicacid/N-n-butyl-p-hydroxybenzamide/N-n-butylbenzamide=1.0/3.2/1.0 (molarratio), and the number-average degree of polymerization of said oligomerwas n=4.2 in the following formula (9): ##STR5##

The above-described ethylene-methyl acrylate-glycidyl methacrylateterpolymer, the aromatic oligomer having a carboxyl group at oneterminal of the molecule and represented by the above-shown formula,which oligomer has a number-average degre of polymerization n determinedby the chemical decomposition method being n=4.2, and a low-densitypolyethylene (LDPE) L-708 (MI at 190° C. under a load of 2.16 kg=8 g/10min; Tg=-115° C.) produced by Sumitomo Chemical Industries Co., Ltd. wasmelt mixed in the ratios shown in Table 1 and reacted withtriparatolylphosphine as catalyst by using Laboplastomill ME-15 mfd. byToyo Seiki Seisaku-sho, Ltd. and furnished with a R-60 mixer and rollertype blades, at 280° C. and 120 r.p.m. for 10 minutes.

MI's of the kneaded products at 260° C. under a load of 10 kg are shownin Table 2. Also, each of the kneaded products was worked into a 2.1 mmthick pressed sheet at 280° C. under a pressure of 50 kg/cm², and thetest pieces for determining the various properties were cut out fromsaid pressed sheet, and the properties were determined. The results areshown in Table 2.

The graft efficiency of the obtained graft copolymer was analyzed andcalculated by a method described below. 500 mg of the obtained graftcopolymer had its aromatic oligomer portion decomposed by theabove-described chemical decomposition method in 40 ml ofN-methylpyrrolidone and 10 ml of n-butylamine. The ethylene-methylacrylate-glycidyl methacrylate copolymer was precipitated in 500 ml ofmethanol to remove it, and after filtration, the filtrate wasconcentrated by an evaporator and, after removing methanol and excessn-butylamine, further filtered by a membrane filter with a pore size of0.45 microns to prepare a test sample.

This sample was analyzed by high performance liquid chromatography usingthe same techniques as described above, and the respective decomposedcomponents were quantified. Calculations can be made from the ratio ofN-n-butylbenzamide to p-hydroxybenzamide decomposed from the aromaticoligomer portion.

More specifically, when the ratio of p-hydroxybenzoic acid toN-n-butylbenzamide quantified as decomposed components is expressed as##EQU1## the amount of the aromatic oligomer reacted as y (g) and theamount of the ethylenemethyl acrylate-glycidyl methacrylate copolymerused as Z (g), the graft efficiency can be calculated as follows.

When the ratio of the aromatic oligomer reacted to the ethylene-methylacrylate-glycidyl methacrylate copolymer is expressed as G₁, G₁ is givenas follows: G₁ =(1-x)×100 (%), and when the rate of reaction of theepoxy group of the ethylene-methyl acrylate-glycidyl methacrylatecopolymer is expressed as G₂, G₂ is given as follows: ##EQU2##

When G₂ was determined for Examples 1 and 2 and Comparative Example 1 inthe manner described above, it was 75%, 70% and 78%, respectively.

Examples 4-9 and Comparative Example 2

Kneading and reaction were carried out under the same kneadingconditions as Examples 1-3, with triphenylphosphine as catalyst, byusing, in place of LDPE used in Examples 1-3, polypropylene (PPr),NORBRENE® Y101 (MI (at 230° C. under 2.16 kg)=12 g/10 min; Tg=-13° C.;produced by Sumitomo chemical Co., Ltd.), ethylene-propylene copolymer,ESPRENE® E-150P (MI (at 230° C. under 2.16 kg)=4.0 g/10 min; Tg=-59° C.;ethylene content: 77 wt %; propylene content: 23 wt %; produced by thesame company), ethylene-propylene copolymer, ESPRENE® E-201 (MI (at 230°C. under 2.16 kg)=1.5 g/10 min; Tg=-63° C.; ethylene content: 46 wt %;propylene content: 54 wt %; produced by the same company), andethylene-methyl acrylate copolymer, ESPRENE® EMA 2602 (MI (at 190° C.under 2.16 kg)= 3.3 g/10 min; Tg=-41° C.; ethylene content: 46 wt %;methyl acrylate content: 54 wt %; produced by the same company), in thecompositions shown in Table 1.

The properties of the kneaded products were evaluated according toExamples 1-3. The results are shown in Table 2.

Examples 10 and 11 and Comparative Examples 3 and 4

An ethylene-methyl acrylate-glycidyl methacrylate terpolymer(ethylene/methyl acrylate/glycidyl methacrylate=38.7/59/2.3 (ratio byweight); MI at 190° C. under a load of 2.16 kg=8.7 g/10 min) wasobtained according to the method described in Japanese PatentApplication Kokai No. 61-127709, Example 5.

The glass transition temperature of this polymer as determined by themethod described in Example 1 was -31.5° C. Also, the weight loss onheating curve of this polymer was determined by the same method as usedin Example 1, from which it was found that this polymer was thermallystable to a temperature close to 350° C.

Then an aromatic oligomer having a carboxyl group at one terminal of themolecule was synthesized according to the method of Example 1 by usingbenzoic acid, parahydroxybenzoic acid and acetic anhydride (in a molarratio of 1:1.8:2.0) as starting materials, then pulverized and washedwith methanol in the same way as in Example 1 to obtain a purifiedoligomer. The flow temperature of this purified oligomer was 168° C.,and its number-average degree of polymerization as determined by theabove-described chemical decomposition method was 3.68. Then weight losson heating of this purified oligomer was measured in the same way asExample 1, from which it was found that this polymer was stable to atemperature close to 300° C.

The above-described ethylene-methyl acrylate-glycidyl methacrylateterpolymer, the aromatic oligomer having a number-average degree ofpolymerization n as determined by the chemical decomposition method of3.68 and possessing a carboxyl group at one terminal of the molecule,and a low-density polyethylene (LDPE) L-708 used in Example 1 or apolypropylene (PPr) NORBRENE® AZ-564 (MI (at 230° C. under 2.16 kg)=30g/10 min) produced by Sumitomo Chemical Industries Co., Ltd. were meltkneaded and reacted, using triparatolylphosphine as catalyst, in thecomposition shown in Table 3, by using Laboplastomill 20R-20 (mfd. byToyo Seiki Seisaku-sho) equipped with a R-60 mixer and roller typeblades, at 280° C. and 200 r.p.m. for 5 minutes (3 minutes inComparative Example 4). The properties of the kneaded products wereevaluated according to Examples 1-3. The results are shown in Table 4.

Examples 12 and 13 and Comparative Example 5

An aromatic oligomer having a carboxyl group at one terminal of themolecule was synthesized according to the method described in Example 1by using benzoic acid, parahydroxybenzoic acid and acetic anhydride (ina molar ratio of 1:3.5:3.85) as starting materials, and then pulverizedand washed with methanol in the same way as in Example 1 to obtain apurified oligomer. The flow temperature of this purified oligomer was243° C. and its number-average degree of polymerization as determined bythe above-mentioned chemical decomposition method was 5.90. Then weightloss on heating of this purified oligomer was measured in the same wayas Example 1, from which it was found this polymer was stable to atemperature close to 300° C.

This purified oligomer, the ethylene-methyl acrylate-glycidylmethacrylate terpolymer described in Examples 10 and 11, LDPE L-708 andPPr AZ-564 were melt kneaded, using triparatolylphosphine as catalyst,in the compositions shown in Table 3 under the same conditions asExample 9. The physical properties of the obtained kneaded products wereevaluated according to Example 1-3. The results are shown in Table 4.

Comparative Example 6

The ethylene-methyl acrylate-glycidyl methacrylate terpolymer used inExample 10 and a low-density polyethylene (LDPE) L-708 used in Example 1were melt kneaded in the compositions shown in Table 3 by the samemethod as used in Example 10. The properties of the obtained kneadedproducts were evaluated according to Examples 1-3. The results are shownin Table 4.

As for MI, it was greater than 100 under the conditions of 260° C. and10 kg loading. When it was measured at 190° C. under a load of 2.16 kg,it was 11.8.

Referential Comparative Example 1

An aromatic oligomer having a carboxyl group at one terminal of themolecule was synthesized according to the method of Example 1 by usingbenzoic acid, parahydroxybenzoic acid and acetic anhydride (in a molarratio of 1:1:1.1) as starting materials. The flow temperature of thesynthesized aromatic oligomer was 89.7, and its number-average degree ofpolymerization as determined by the chemical decomposition method was1.52.

When weight loss on heating of this aromatic oligomer was measured inthe same way as Example 1, it showed loss of about 2.3 wt %/10° C.almost linearly in the temperature range of 120°-360° C., indicatingthat this polymer was thermally unstable.

Thus, when using this aromatic oligomer, it can not be expected that theproduced graft copolymer would show a satisfactory thermal resistance,and there can only be obtained a graft copolymer which is thermallyunstable.

                                      TABLE 1                                     __________________________________________________________________________    Kneading composition                                                          Ethylene-methyl                                                               acrylate-glycidyl                                                             methacrylate                                                                  terpolymer     Aromatic                                                                             Polyolefin   Catalyst                                   (g)            oligomer (g)                                                                         Kind   Amount (g)                                                                          Kind       Amount (mg)                     __________________________________________________________________________    Example 1                                                                           40.5     4.5    LDPE L-708                                                                           5.0   Triparatolylphosphine                                                                    45                              Example 2                                                                           36.9     4.1    "      8.2   "          41                              Example 3                                                                           34.2     3.8    "      11.4  "          38                              Comp. 45.0     5.0    --     --    "          50                              Example 1                                                                     Example 4                                                                           40.5     4.5    PPr Y-101                                                                            5.0   Triphenylphosphine                                                                       45                              Example 5                                                                           36.9     4.1    "      8.2   "          41                              Example 6                                                                           31.5     3.5    E-150P 15.0  "          100                             Example 7                                                                           31.5     3.5    E-201  15.0  "          100                             Example 8                                                                           40.5     4.5    EMA2602                                                                              5.0   "          100                             Example 9                                                                           31.5     3.5    "      15.0  "          100                             Comp. 45.0     5.0    --     --    "          50                              Example 2                                                                     __________________________________________________________________________

                                      TABLE 2                                     __________________________________________________________________________    MI                                                                            (260° C., Compression set (%)                                                                       Elonga-                                                                              Breaking                                                                             100%   Perma-                      10 kg)      Shore A                                                                            25° C.,                                                                    100° C.,                                                                   160° C.,                                                                   tion at                                                                              strength                                                                             modulus                                                                              nent set                    (g/10 min)  hardness                                                                           22 hr                                                                             70 hr                                                                             22 hr                                                                             break (%)                                                                            (kg/cm.sup.2)                                                                        (kg/cm.sup.2)                                                                        (%)                         __________________________________________________________________________    Example 1                                                                           35.0  24   37.3                                                                              --  57.2                                                                              800    33.0   7.4    30                          Example 2                                                                           60.2  26   37.9                                                                              --  62.1                                                                              850    46.4   13.9   80                          Example 3                                                                           84.5  34   47.1                                                                              --  56.5                                                                              800    51.0   23.4   130                         Comp. 32.4  19   38.0                                                                              --  56.0                                                                              1200   54.7   5.3    50                          Example 1                                                                     Example 4                                                                           45.8  26   --  75.6                                                                              --  900    32.0   10.4   50                          Example 5                                                                           92.1  40   --  87.1                                                                              --  800    29.0   22.3   68                          Example 6                                                                           3.2   26   --  62.1                                                                              --  Not measured                                                                         Not measured                                                                         Not measured                                                                         Not measured                Example 7                                                                           5.1   19   --  45.5                                                                              --  450    20.6   4.5    10                          Example 8                                                                           5.3   18   --  44.7                                                                              --  850    30.5   5.4    30                          Example 9                                                                           77.4  16   --  75.2                                                                              --  1250   16.4   3.2    60                          Comp. 2.8   22   --  69.5                                                                              --  825    33.0   6.0    35                          Example 2                                                                     __________________________________________________________________________

                                      TABLE 3                                     __________________________________________________________________________    Ethylene-methyl                                                               acrylate-glycidyl                  Catalyst                                   methacrylate   Aromatic                                                                             Polyolefin   (triparatolyl-                             terpolymer (g) oligomer (g)                                                                         Kind   Amount (g)                                                                          phosphine) (mg)                            __________________________________________________________________________    Example 10                                                                          36       4      LDPE L-708                                                                           10    100                                        Example 11                                                                          36       4      PPr AZ-564                                                                           10    100                                        Comp. 45       5      --     --    100                                        Example 3                                                                     Comp. 40       10     --     --    100                                        Example 4                                                                     Example 12                                                                          32       8      LDPE L-708                                                                           10    100                                        Example 13                                                                          34       6      PPr AZ-564                                                                           10    100                                        Comp. 40       10     --     --    100                                        Example 5                                                                     Comp. 40       --     LDPE L-708                                                                           10    --                                         Example 6                                                                     __________________________________________________________________________

                                      TABLE 4                                     __________________________________________________________________________    MI                 Compression                                                                          Elongation                                                                          Breaking                                                                           100% Permanent                           (260° C., 10 kg)                                                                     Shore A                                                                            set (100° C.,                                                                 at break                                                                            strength                                                                           modulus                                                                            set                                 (g/10 min)    hardness                                                                           70 hr) (%)                                                                           (%)   (kg/cm.sup.2)                                                                      (kg/cm.sup.2)                                                                      (%)                                 __________________________________________________________________________    Example 10                                                                          55.8    29   74.6   850   30.5 13.4 150                                 Example 11                                                                          140     25   82.0   975   22.4 11.8 90                                  Comp. 71.0    12   73.3   1200  25.8 3.8  50                                  Example 3                                                                     Comp. 0.24    20   43.1   375   27.8 6.3  10                                  Example 4                                                                     Example 12                                                                          81.1    30   82.5   600   34.3 19.8 140                                 Example 13                                                                          158     38   76.7   416   26.7 22.1 35                                  Comp. 96.2    18   87.5   1050  23.4 5.9  45                                  Example 5                                                                     Comp. >100    10   100    1025  1.3  2.4  250                                 Example 6                                                                     __________________________________________________________________________

INDUSTRIAL APPLICABILITY

The thermoplastic elastomer composition of this invention, as describedabove, shows the behavior of an excellent rubber elastomer even at hightemperatures and is also excellent in thermal resistance, so that it canbe used as material for various types of hoses such as oil cooler hose,air duct hose, power stearing hose, control hose, oil return hose,heat-resisting hose, etc., material for various types of seals such asvarious oil seals, O-rings, packings, gaskets, etc., and material forvarious kinds of diaphgrams, rubber plates, belts, oil level gages, hosemasking, sound insulators, etc. Thus, the scope of application of thisinvention is very wide.

We claim:
 1. A thermoplastic elastomer composition comprising athermoplastic graft copolymer of which main chain is constituted by apolymer having a glass transition temperature of 10° C. or below andside chain is constituted by an aromatic oligomer having a flowtemperature between 100° C. and 400° C., and an olefinic polymer whereinthe flow temperature is the temperature at which the oligomer shows amelt viscosity of 48,000 poises when the oligomer is melted by heatingat a rate of 4° C./min and extruded from a nozzle of 1 mm in innerdiameter and 10 mm in length under a load of 100 kg/cm² and wherein aratio of the polymer having the glass transition temperature of 10° C.or below to the aromatic oligomer is 99:1 to 50:50 by weight.
 2. Athermoplastic elastomer composition according to claim 1, wherein theside chain of the thermoplastic graft copolymer is constituted by anaromatic oligomer having a flow temperature of 150°-350° C.
 3. Athermoplastic elastomer composition according to claim 1, wherein thearomatic oligomer contains 50% by weight or more of a structural unitsrepresented by the general formula (1): ##STR6## wherein X is selectedfrom O and S, and the structural unit containing O and the structuralunit containing S may both be contained in one oligomer; and Ar isselected from the general formulae (2), (3) and (4): ##STR7## wherein R¹and R² are each selected from an alkyl group having 1-3 carbon atoms anda phenyl group; R¹ and R² may be a same or different groups, and thedifferent groups may be attached to one benzene ring; and p and q areeach an integer of 0-2.
 4. A thermoplastic elastomer compositionaccording to claim 1, wherein the number-average degree ofpolymerization of the aromatic oligomer is 2 to
 10. 5. A thermoplasticelastomer composition according to claim 1, wherein the number-averagemolecular weight of the aromatic oligomer is 300 to 1,500.
 6. Athermoplastic elastomer composition according to claim 1, wherein theglass transition temperature of the main chain of the thermoplasticgraft copolymer is 0° C. or below.
 7. A thermoplastic elastomercomposition according to claim 1, wherein the main chain of thethermoplastic graft copolymer is a polymer selected from the groupconsisting of acrylic ester polymer, styrene-butadiene copolymer and itshydrogenated product, styrene-isoprene copolymer and its hydrogenatedproduct, polybutadiene, polyisoprene, ethylene-propylene copolymer,ethylene-propylene-diene copolymer, acrylonitrile-butadiene copolymerand its hydrogenated product, polychloroprene, ethylene-acrylic estercopolymer, chlorosulfonated polyethylenes, polyorganosiloxanes andpolyphosphazene.
 8. A thermoplastic elastomer composition according toclaim 1, wherein the olefinic polymer is a polymer selected from thegroup consisting of polyethylene, polypropylene, ethylene-propylenecopolymer, ethylene-butene copolymer, ethylene-propylene-dieneterpolymer, ethylene-methyl acrylate copolymer and ethylene-ethylacrylate copolymer.
 9. A thermoplastic elastomer composition accordingto claim 1, wherein the weight ratio of the graft copolymer to theolefinic polymer is 99:1 to 50:50.
 10. A process for preparing athermoplastic elastomer composition set forth in claim 1, whichcomprises reacting a polymer having a glass transition temperature of10° C. or below and possessing a functional group reactable withcarboxyl group, and an aromatic oligomer having a flow temperature of100° C. or above and possessing a carboxyl group at one terminal of themolecule, thereby obtaining a graft copolymer, and mixing said graftcopolymer with an olefinic polymer.
 11. A thermoplastic elastomercomposition comprising a thermoplastic graft copolymer of which mainchain is constituted by a polymer having a glass transition temperatureof 10° C. or below and side chain is constituted by an aromatic oligomerhaving a flow temperature between 100° C. and 400° C., and an olefinicpolymer wherein the flow temperature is the temperature at which theoligomer shows a melt viscosity of 48,000 poises when the oligomer ismelted by heating at a rate of 4° C./min and extruded from a nozzle of 1mm in inner diameter and 10 mm in length under a load of 100 kg/cm² andwherein a ratio of the polymer having the glass transition temperatureof 10° C. or below to the aromatic oligomer is 99:1 to 50:50 by weight,and said elastomer composition having a Shore A hardness of 40 or less.